Research Of CAPG Drilling Fluid Resembling Oil-based Fluids

Shale instability is the most common accident in the underground drilling Most happen where the shale prone to be hydrated when meet with water.The traditional water-based drilling fluids cannot inhibit the shale hydration effectively.The traditional solution is to adopt the oil-based drilling fluids.However,the oil-based ones are expensive and can pollute environment,so it is not so popular.As a result,a kind of water-based drilling fluid whose performance is similar with the oil-based one is a must now.The cationic alkyl polyglycoside(CAPG)is a kind of good inhibitor and lubricant.It can provide a better solution when the fluid needs to be a better inhibition,a reservoir protection and environmentally friendly.The paper combines with geological features of the oil field.Through trials and errors,the optimal drilling fluid is finally got.An evaluation of the performance is also made.It makes a great practical significance for oilfield drilling.First,the concentration of CAPG is determined by some experiments.Then throu gh the experiments the thickener,fluid loss control agents,inhibitors,blocking agents i s chosen which can match with CAPG preferably.At last,according to the orthogonal experiment,the formulations of CAPG drilling fluid is determined:50%CAPG+1%bent onite+0.1%XC+0.05%HV-CMC+0.1%LV-CMC+1.5%CMS+3%palygorskite+3%WLP+3.5%NaOH.Experiments show that the CAPG drilling fluid system has a good rheology,inhibition,lubrication,environment-friendly,the cuttings recovery rolling up to 99.05%,temperature resistant to 150℃,120℃With good performance for 96 h,lubrication factor up to 0.052,a good performance with saturated salt water,anti-contaminated drill cuttings capacity up to 20%,water resistant to 40%,oil resist to 20%,EC50(15min)126700 ppm.The performance of system is close to the oil-based drilling fluid.In the last part,we take a preliminary study about the mechanism of CAPG in the system,in different aspects of inhibition,temperature resistance,lubricity,fluid loss and reservoir protection.